In optical communication systems, optical amplifiers are used to improve the power level of optical signals. At the transmitter side of the communication system, a booster is used to amplify the optical signal power before the signal is launched into the optical fiber. At the receiver side, a pre-amplifier is used to amplify the received signal power to a sufficient level for the receiver sensitivity. The boosters and pre-amplifiers also compensate for component: losses added as optical communication systems become more sophisticated, such as dispersion compensation modules.
In a multi-channel communication system, such as systems that employ wavelength division multiplexing (WDM), a single booster and a single pre-amplifier may be used for all channels. However, as the number of channels being used increases, it becomes more difficult for a single multi-channel booster to achieve the required output power for all channels. Furthermore, as the data rate of optical communication systems increases, the required receiver power for each receiver increases. A single multi-channel pre-amplifier may have difficulty achieving the required receiver power for the receivers for all channels.
There is therefore a trend towards using a single booster and a single pre-amplifier for each channel. For each transmitter, one booster is placed between the transmitter and the multiplexer. In this way, each booster amplifies the signal strength of only one channel. For each receiver, one pre-amplifier is placed between the demultiplexer and the receiver. A single-channel tuneable dispersion compensation module/polarization mode dispersion compensator may be placed between each pre-amplifier and the corresponding receiver.
The use of single-channel boosters and single-channel pre-amplifiers allows the required signal strengths to be obtained, even at higher communication speeds (such as 40 Gbps). However the use of multiple single-channel boosters and single-channel pre-amplifiers can be costly. The greater number of components required in using many boosters and pre-amplifiers can be expensive, in terms of both cost and power consumption.